Display device for aircraft and method for displaying detected threats

ABSTRACT

This invention concerns a display device for aircraft comprising a display surface ( 15 ) that has a punctual marking ( 11 ) arranged so as to represent the pilot&#39;s own airplane and one or more threat markings, each of which is arranged so as to represent a direction to an associated detected threat. The display device is characterized in that each threat marking comprise an indicator ( 14, 15 ) that contains information about the time to the associated threat, and in that it is arranged so as to present, on a display surface ( 15 ), a current time discrepancy relative to a planned mission and a remaining amount of fuel relative to the planned mission. The invention also concerns a method for presenting one or more detected threats in relation to an aircraft.

TECHNICAL AREA

[0001] This invention concerns a display device for aircraft accordingto the preamble to claim 1.

[0002] The invention also concerns a method for displaying one or moredetected threats in relation to an aircraft according to the preamble toclaim 1.

STATE OF THE ART

[0003] Pilots of civil airplane have previously been dependent on tocertain degree of visual contact with nearby airplanes, advice fromground-based traffic control stations to avoid collisions in theairspace, and on sensors (e.g. radar) carried in the airplane. However,systems exist today that include transponders that can be implemented inairplanes, and which can aid in the pilot in obtaining informationconcerning the positions of nearby passing airplane in relation to thepilot's own airplane. These transponders periodically send out querysignals into the surrounding airspace. The transponders of nearbyairplanes are arranged so as to respond to said query signals byemitting a response signal containing information about the altitude ofsaid nearby airplanes. The querying transponder receives the responsesignal and measures the time that has elapsed between the transmissionof the query signal and the reception of the response signal. Based onthe information in the response signal and the measured time, data suchas the altitude and rate of climb/descent of the nearby airplane arecalculated, as are its range and changes in the range to the nearbyairplane.

[0004] U.S. Pat. No. 4,914,733 concerns an instrument in an airplanecockpit, which instrument is arranged so as to present the calculateddata and is intended for use as a decision-making aid for the pilot ofthe airplane. The instrument includes a display in which the center ofthe display surface represents the position of the pilot's own airplane.Surrounding airplanes are presented on the display as symbols positionedrelative to the center of the display surface in such a way that thedirection of and distance between the pilot's own airplane and thesurrounding airplanes are made clear. The symbols for the surroundingairplanes are realized differently based on a characterization of eachairplane that is in turn based on the aforedescribed calculated data, sothat a first symbol type represents a non-threatening airplane, a secondsymbol type represents a potentially threatening airplane and a thirdsymbol type represents a threatening airplane that requires that thepilot take steps to avoid a collision. An indication generated by theairplane equipment as to what action is appropriate for the pilot totake (e.g. CLIMB, DESCEND, DO NOT CLIMB, DO NOT DESCEND) is associatedwith the symbol for a threatening plane.

[0005] U.S. Pat. No. 5,506,587 describes a more modern transpondersystem.

[0006] The transponder systems described in U.S. Pat. No. 4,914,733 andU.S. Pat. No. 5,506,587 are not adequate for military applications,where the threat may consist of, e.g. a hostile airplane. Such hostileairplanes will seek to conceal their existence/identity, and are notinterested in giving their position, which is indeed the underlyingbasis of the transponder system. Furthermore, the range informationprovided by the instrument provides far too limited decision-makingsupport for military applications.

[0007] In addition to being equipped with transponder systems, militaryairplanes are also equipped with some type or types of sensor system todetermine position/direction of one or more threats, and also toidentify these threats. These sensor systems can be designed in a numberof different ways.

[0008] A first type of sensor system is based on radar, wherein thepilot's own plane emits radar signals and receives reflected radarsignals and, based on the properties of the received signals, determinesthe range and direction of the object from which the radar signals arebeing reflected. In addition, different types of airplane have differentradar signatures, thereby enabling their identification. Identifying anairplane type from the radar signature of an object also makes itpossible to make assumptions as to the types of weapons with which theplane is armed.

[0009] A second type of sensor system includes radar interceptionreceivers that passively “listen” for radar signals to which the pilot'sown plane is exposed. Based on the properties of the received radarsignals, it is possible to make an assumption as to the type of radarfrom which the signals are being received. Based on this information, itis then possible to say with some degree of probability which weaponsystem is engaged. Based on a knowledge of the weapon system inquestion, it is then further possible to assume the weapon type andperformance with some degree of probability. A third type of sensorsystem comprises different types of IR sensors, such as IRST (InfraRedSearch and Track). A fourth type of sensor system is based ontransponder technology in which position and identity information areobtained from interactive IFF equipment and communications links. Afifth type of sensor system is based on an information exchange, e.g.position and identity information is communicated between airplane vialinks. A sixth type of sensor system is based on information exchangesbetween airplanes and tactical control via links. All these types ofsensor systems, and others, can interact in a multi-sensor system inorder to increase the precision of the input measurements.

SUMMARY OF THE INVENTION

[0010] The invention is intended to provide a concentrated overallpresentation of selected threats that have been, e.g.detected/identified via a. sensor system arranged on an aircraft.

[0011] This has been achieved by means of a display device for aircraftcomprising a display surface that presents a symbol comprising of anouter edge surrounding a symbol center, wherein the symbol center marksthe airplane and where one or more threat markings are positioned inrelation to the outer edge in such a way that each of them indicates adirection to an associated detected threat. The display device ischaracterized in that each threat marking comprises an indicator thatextends from the outer edge toward the symbol center and whose length ischosen so that the distance between the end of the indicator and thesymbol center represents a predicted time until it is estimated that thepilot's own airplane will reach the threat represented by the respectivethreat marking, and in that the display device is arranged so that thedisplay surface presents a current time discrepancy relative to aplanned mission, and the amount of fuel left in relation to the plannedmission.

[0012] The threat characteristically represents a threat zone surroundedby a threat boundary, wherein the pilot's own airplane is assumed toreach the threat when the threat boundary is transgressed. The threatmay consist of, e.g.:

[0013] an airplane that is on a course toward the pilot's own aircraft,

[0014] a weapon on an airplane that is located within the effectiverange of said weapon,

[0015] the effective range of ground or sea-based antiaircraft systems,or

[0016] a solid object in the form of a building, mast or rock wall.

[0017] The aircraft is, e.g. a military airplane, primarily an attack orreconnaissance airplane. The planned mission may be a mission that hasbeen planned in detail with breakpoints, and with precisely plannedaltitudes and speeds for each subsection between two breakpoints. Themission is thus divided into a number of continuous subsections thattogether form a polygon in which each section has its own associatedaltitude and speed. During the performance of a such a mission, theinformation presented by the display means is the very information thatthe pilot needs in order to make quick decision as to how he/she shouldact vis-a-vis the various problems that can arise in the form of thetypes of threats described above, or “internal” threats in the form ofdelays related to a timetable or shortage of fuel. The aforedescribedthreats and internal threats are the factors that limit the pilot'sfreedom of action in connection with decision-making. These factors arealso covariant. This means: that, for example, if the pilot increasesspeed to keep to the timetable, this will lead to increased fuel use,which could in turn mean that there will not be enough fuel for theplanned mission, insofar as the fuel supply is not very good in relationto the mission. In another example where the pilot is planning to changethe planned mission (replanning) by taking an alternate flight path tocircumvent an external threat, the display device will provide theinformation that the pilot needs to make a quick and correct decision,i.e. the display device will indicate whether the timetable and fuelstatus permit such an evasive maneuver. It is thus extremelyadvantageous to display, along with directions to threats, the timeuntil the threat, the time available to complete the mission in relationto the timetable, and the fuel status in relation to the plannedmission.

[0018] The aircraft has been described above as an airplane, in whichcase the display device is arranged in connection with the cockpitinstrumentation. In an alternative embodiment in which the aircraft isunmanned, the display device is not arranged in connection with theaircraft, but rather deployed in, e.g. a ground-based station that is incontact with the aircraft.

[0019] Preferred embodiments exhibit one or more of the characteristicfeatures specified in subordinate claims 2-10.

[0020] The invention also includes a method for displaying one or moredetected threats in relation to an aircraft, wherein each and every oneof the detected threats is represented by a threat marking on a displaysurface, and wherein the aircraft is placed at a center surrounding byan outer edge, and wherein a direction to each threat is designated bythe location of the associated threat marking relative to the outeredge. Each threat marking is represented by an indicator that extendsfrom the outer edge toward the symbol center, whereupon the length ofthe indicator is chosen so that the distance between the end of theindicator and the symbol center represents the time left until theassociated threat is reached. A current time discrepancy relative to aplanned mission is presented on the display surface, as is the amount offuel left in relation to the planned mission.

BRIEF DESCRIPTION OF FIGURES

[0021]FIG. 1 shows an example of an airplane cockpit with an instrumentaccording to the invention.

[0022]FIG. 2 shows an example of a system solution with an instrumentaccording to the invention.

[0023]FIG. 3 shows the instrument according to a first embodiment.

[0024]FIG. 4 shows the instrument according to a second embodiment.

[0025]FIG. 5 shows the instrument according to a third embodiment.

PREFERRED EMBODIMENTS

[0026] In FIG. 1, reference number 1 designates a device placed in acockpit of, e.g. a military attack airplane. The device 1 has a displaysurfaced 15 realized using, e.g. LCD, CRT or VRD technology andinstalled, e.g. inside the front windshield of the cockpit in aso-called head-up 16, or in a so-called head-down display 17. In theembodiment shown in the figure, the head-down display 17 and the head-updisplay 16 have been installed in a panel 18, and the device 1 isincluded in the head-down display 17. The display surface 15 mayalternatively be integrated with the airplane pilot's helmet (VRDtechnology). The device 1 is intended to display information via thedisplay surface 15 for use as a decision-making aid during combatmissions.

[0027] In FIG. 2, reference number 5 designates a unit in which amission that has been planned in detail is input and stored withaltitudes, positions and speeds for the entire mission preciselyplanned. The mission is divided into, e.g. a number of continuoussections that together form a polygon in which each section has anassociated altitude and speed.

[0028] The mission unit 5 is connected to a unit 6 that calculates fuelconsumption for the completion of the planned mission in relation to theavailable fuel. From the airplane fuel system the fuel-calculating unit6 has access to information as to how much fuel is left. Together withinformation available from the mission unit 5 and the fuel system, theunit 6 calculates how much fuel is expected to be needed for theremainder of the mission, and compares the expected fuel consumptionwith the actual supply to generate a value ΔF that indicates thedifference between the expected consumption and the actual supply.

[0029] The mission unit 5 is further connected to a unit 7 thatdetermines the current time status of the pilot's own airplane inrelation to a timetable for the planned mission. The timetable iscalculated using mission data input into the mission unit 5. In a simpleembodiment the unit 7 retrieves the position of the pilot's plane via anavigation system (not shown) included in the plane, compares theexpected position specified in the mission with the actual positionprovided by the navigation system and calculates how much time it willtake to travel between the actual position of the airplane and theexpected position, based on the flight altitudes and airspeeds enteredfor the mission, in order to generate a value ΔT that indicates the timedifference between the expected position according to the schedule forthe mission, and the actual position. The navigation system may compriseinertial navigation, GPS, air data, sensors, etc., and is arranged so asto indicate the position, altitude, direction of flight and attitude ofthe plan relative to a defined coordinate system. In one example themission unit 5 is connected to a diskette unit connected to a computer,wherein the mission is stored on a diskette. In this example thecomputer contains the units 6 and 7 and is equipped with an, interfaceto receive the necessary information from the fuel system and navigationsystem of the airplane.

[0030] Reference number 2 designates sensors connected to a sensorsystem 3 for detecting, determining the position of and identifyingthreats. We have noted above that such sensor systems can beradar-based, radar interception receiver-based, tactical control-based,link-based or IR-based, and that they provide position/direction andidentity information for each detected threat. We will not describe sucha sensor system in detail here, but simply assume its existence.

[0031] The sensor system 3 is connected to a calculating unit 4 fordetermining threat boundaries based on the identified threats, and forcalculating times until these threat boundaries will be reached. Anidentity in the form of, e.g. a number and/or letter combination isassigned to each threat. If a threat is unidentified, then only thedirection to the threat can be displayed. The calculating unit 4 willthen calculate, based on the determined threat boundaries, the timeuntil the pilot's own, plane will reach the respective threat boundary,based on the current speed and direction the pilot's own plane.

[0032] From the calculating unit 6 the device 1 retrieves the differenceΔF between the expected fuel consumption for the remainder of themission and the actual fuel supply. From the time-calculating unit 7 thedevice 1 retrieves the difference ΔT that indicates the extent to whichthe flight is ahead of or behind the timetable for the planned mission.From the sensor system 3 the device 1 retrieves the direction to eachand every one of the threats and, from the calculating unit 4, theestimated time until the pilot's own plane will reach the threatboundary of the threat zone that each threat represents. The device 1presents the retrieved information on the display surface 15 asdescribed below.

[0033] In FIG. 3 the instrument 1 is displaying a symbol 9 on itsdisplay surface, which symbol has an outer edge 10. The outer edge 10 iscircular in the example shown, but examples in which the outer edge iselliptical, square or rectangular are also conceivable.

[0034] The center 11 of the circle 10 represents the position of thepilot's own airplane. Indicators 14, 15 extend from the edge of thecircle 10 to the center 11. The locations on the circle edge from whichthe indicators start are controlled by the direction to the threat asdetermined by the sensor system 3, and represent a projection, in thehorizontal plane, of the direction to the threat in relation to thedirection of flight of the pilot's own plane. In the example shown inFIG. 3, the direction of flight of the pilot's own plane is straight upin the circle (0°). The distance between the center 11 and the end ofeach indicator represents the estimated time until the threat will bereached, which time is retrieved from the calculating unit 4. If thethreat is approaching the pilot's own airplane, this will be obvious tothe pilot in that the indicator will creep closer to the center of thecircle, which of course represents the position of the pilot's ownplane. If, on the other hand, the threat is withdrawing, this will alsobe obvious to the pilot of the plane, in that the indicator will shrinkin length, whereupon its end will withdraw from the center of thecircle. Note that these indicators provide a snapshot of the resultsfurnished by the sensor system 3 and the calculating unit 4. If, forexample, the sensor system 3 re-identifies a threat after a period oftime, its threat boundaries will be affected instantaneously, as willthe length of its associated indicator. In FIG. 3 each indicator 14, 15is associated with an identity L10, M7, as described above. Theseidentities tell the pilot which type of threat each of the indicators14, 15 represents.

[0035] In one embodiment threats are marked based on the time until thethreat boundary will exceed a pre-selected value on the circle edge at apoint that corresponds to the direction of the threat. The pre-selectedvalue thus indicates, in this embodiment, the maximum time interval,which will be represented by an indicator. In FIG. 3 such a threat ismarked with a dot 8 and associated with an identity L7. In analternative embodiment a specified number of threats are marked with anindicator 14, 15, while other threats are marked with a dot 8. Forexample, the 5, 8, 10 or 12 most urgent threats are marked with anindicator. In yet another alternative embodiment a priority reflecting adegree of “danger” is assigned to each type of threat. According to thisembodiment, a pre-selected number of threats is marked with an indicatoron the basis of their threat priorities. For example, the 5, 8, 10 or 12highest priority or most dangerous threats are marked with an indicator14, 15, while other threats are marked with, e.g. a dot 8. In yetanother alternative embodiment each indicator 14, 15 containsinformation about the priority of its corresponding threat in that, e.g.the indicators are realized with different intensities.

[0036] In an alternative embodiment (not shown), each indicator extendsfrom the center 11 toward the circle edge 10, and the distance betweenthe end of the indicator and the edge 10 represents the estimated timeto the threat.

[0037] Parallel with the circle edge 10 there runs a first curved bar 12that indicates whether the flight is ahead of or behind the timetablefor the input mission, as calculated by the calculating unit 7. When theΔT value furnished by the calculating unit 7 indicates that the pilot istraveling faster than specified in the mission, the bar will extendupward along the edge of the circle from a zero position at 270°, asshown in FIG. 3. The length of the bar is proportional to the amount oftime by which the flight is ahead of the timetable for the plannedmission. If, on the other hand, the flight is behind the timetable forthe mission, the bar will extend downward along the edge of the circlefrom the zero position at 270°. Here the length of the bar isproportional to the amount of time by which the flight is behindschedule. To further clarify the situation, the bar has a pre-selectedfirst color when the pilot is ahead of the timetable specified for themission, and a pre-selected second color when the pilot is behindschedule.

[0038] Along the edge of the circle there runs a second curved bar 13that indicates whether the plane has an surplus or deficit of fuel inrelation to the rest of the mission. The direction and length of thisbar are thus determined by the value ΔF provided by the fuel-calculatingunit 6. When there is a surplus of fuel, the bar 13 will extend upwardrelative to the index for the zero point along the edge of the circlefrom a zero position at 90%. The length of the bar is proportional tohow much surplus fuel is available. If, on the other hand, the remainingfuel is not sufficient for the rest of the mission, as shown in FIG. 3,the bar 13 will extend down relative to the index for the zero pointalong the edge of the circle. The length of the bar will be proportionalto the magnitude of the fuel deficit. To further clarify the situation,the bar has a pre-selected first color when there is a surplus of fuel,and a pre-selected second color when there is a fuel deficit.

[0039] The bars 12, 13 extend along the periphery of the circle 10 inFIG. 3. However, many other ways of representing time and fuelconsumption in relation to the mission are conceivable. For instance, inFIG. 4 the first bar 12 has its zero point at the edge, at 270° in thefigure, and extends toward the center when the time discrepancy isnegative, i.e. the flight is behind the timetable for the plannedmission, and in the opposite direction when the time discrepancy ispositive. The second bar 13 also has its zero point on the edge, at 90°in the figure, and extends toward the center when the fuel is notsufficient to complete the entire mission, and in the opposite directionwhen there is surplus fuel. In this way the problem is presented to thepilot in a very clear manner, and the pilot can see by glancing quicklyat the instrument 1 whether bars 12, 13 or indicators 14, 15 are presentin the circle 10.

[0040] The embodiment shown in FIG. 5 is equivalent to the embodimentshown in FIG. 3 except for the realization of the indicators 14, 15. InFIG. 5 each indicator extends all the way from the edge 10 to the center11. The indicators are thicker along a portion of a length equivalent tothe indicators described in connection with FIG. 3 than along theremainder of their length. In this way the distance between the center11 and the end of each thick indicator portion represents the estimatedtime until the threat. If the threat is approaching the pilot's ownairplane, this will be obvious to the pilot in that the thick portion ofthe indicator will creep closer to the center of the circle, which ofcourse represents the position of the pilot's own airplane. If, on theother hand, the threat is withdrawing, this will also be obvious to thepilot of the airplane, in that the length of the thick portion of theindicator will shrink, whereupon the thick end will withdraw from thecenter of the circle. It will be apparent to one skilled in the art thatan indicator that is divided into two portions, with one portion being athick line and the remaining portion being a thin line, could bereplaced by a differently realized divided indicator while retaining thesame function. For example, the indicator could be two-colored.

[0041] We have described above a system comprising a number of unitssuch as the calculating unit 4, the mission unit 5, the fuel-calculatingunit 6 and the time-calculating unit 7. However, it must noted thatthese units need not necessarily be viewed as physically separableparts, and that they may constitute integral parts of a complex system.Each unit can use make use of stored values or values from other units.The ways in which these units are realized are not essential to theinvention; the main issue is that they provide the data that the device1 requires.

1. A display device (1) for aircraft comprising a display surface (15)that presents a symbol (9) comprising of an outer edge (10) surroundinga symbol center (11), wherein the symbol center (11) marks the aircraftand wherein one or more threat markings are positioned in relation tothe outer edge (10) in such a way that each of them indicates adirection to an associated detected threat, characterized in that: eachthreat marking comprises an indicator (14, 15) that extends from theouter edge (11) in the direction toward the symbol center and whoselength is chosen so that the distance between the end of the indicatorand the symbol center represents the time until the associated threat,the display device (1) is arranged so as to present, on a displaysurface (15), a current time discrepancy in relation to a plannedmission and the amount of fuel left in relation to the planned mission.2. A device according to claim 1, characterized in that only thosethreats for which the time to the threat is less than a pre-selectedvalue are assigned an indicator.
 3. A device according to claim 2,characterized in that the outer edge (10) is placed at a distance fromthe symbol center (11) that corresponds to said pre-selected value.
 4. Adevice according to claim 3, characterized in that the outer edge (1) iscircular in shape.
 5. A device according to claim 1, characterized inthat the time discrepancy is presented in the form of a first bar (12)whose length and direction depend on the current time discrepancy.
 6. Adevice according to claim 5, characterized in that the first bar (12) isplaced outside of the symbol (9) and extends along a portion thereof. 7.A device according to claim 5, characterized in that the first bar (12)has its zero point at the outer edge (10) and extends in toward thesymbol center (11) when the time discrepancy is negative, i.e. when theflight is behind a timetable for the planned mission, and in theopposite direction when the time discrepancy is positive.
 8. A deviceaccording to claim 1, characterized in that the amount of fuel left inrelation to the planned mission is presented in the form of a second bar(13).
 9. A device according to claim 8, characterized in that the secondbar is placed outside of the symbol (9) and extends along a portionthereof.
 10. A device according to claim 8, characterized in that thesecond bar (13) has its zero point at the outer edge (10) and extends intoward the symbol center (9) when the fuel is not expected to sufficefor the entire mission, and in the opposite direction when there is asurplus of fuel.
 11. A method for displaying one or more detectedthreats in relation to an aircraft, wherein each and every one of thedetected threats is represented as a threat marking on a display surface(15), wherein the aircraft is placed at a center (11) surrounded by anouter edge (11), and where a direction to each threat is marked by theplacement of the associated threat marking in relation to the outer edge(10), characterized in that: each threat marking is represented by anindicator (14, 15) that extends from the outer edge (10) in thedirection toward the symbol center, wherein the length of the indicatoris chosen so that the distance between the end of the indicator and thesymbol center represents the time until the associated threat, and acurrent time discrepancy in relation to a planned mission and theremaining fuel left in relation to the planned mission are presented ona display surface (15).